An argon ion beam milling process for native AlOx layers enabling coherent superconducting contacts

  1. Lukas Grünhaupt,
  2. Uwe von Lüpke,
  3. Daria Gusenkova,
  4. Sebastian T. Skacel,
  5. Nataliya Maleeva,
  6. Steffen Schlör,
  7. Alexander Bilmes,
  8. Hannes Rotzinger,
  9. Alexey V. Ustinov,
  10. Martin Weides,
  11. and Ioan M. Pop
We present an argon ion beam milling process to remove the native oxide layer forming on aluminum thin films due to their exposure to atmosphere in between lithographic steps. Our cleaning process is readily integrable with conventional fabrication of Josephson junction quantum circuits. From measurements of the internal quality factors of superconducting microwave resonators with and without contacts, we place an upper bound on the residual resistance of an ion beam milled contact of 50mΩ⋅μm2 at a frequency of 4.5 GHz. Resonators for which only 6% of the total foot-print was exposed to the ion beam milling, in areas of low electric and high magnetic field, showed quality factors above 106 in the single photon regime, and no degradation compared to single layer samples. We believe these results will enable the development of increasingly complex superconducting circuits for quantum information processing.
arxiv pdf

leave comment